摘要:

In 1968 Zen and coworkers reported that thep-tolylsulfonyl group could be removed from carbohydrate systems by photochemical reaction (eq 1).1Since then other investigators have used this deprotection process in carbohydrate synthesis.2-10Mechanistic studies11-16have shown that tosylate photolysis is promoted by compounds (e.g., triethylamine) that donate an electron to an excitedp-toluenesulfonate to generate a radical anion (1). This intermediate then fragments to form the anion of the deprotected sugar (Scheme 1). Since generating a radical anion is the central element in this photochemical process, structural changes that impact radical anion formation should influence the reaction. Replacing thep- tolylsulfonyl group with the pentafluorophenylsulfonyl group generates a more stable radical anion (2) because the electronegative fluorine atoms can help stabilize the negative charge. Since we have a continuing interest in the photochemistry of sulfonic acid esters, we synthesized the pentafluorobenzenesulfonates (pentaflates) 3-6 and studied their photochemistry under electron transfer conditions.

ISSN:0732-8303    

DOI:10.1080/07328309508005394

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Sugar losses result when sucrose in highly concentrated solution degrades under heat and other stresses in the factory and refinery and in manufacture of sugar containing products. Impurities such as salts, can increase the thermal degradation rate of sucrose under processing conditions, although literature sources conflict on the extent,2,3,4,5and the mechanism of action has still to be ascertained.

ISSN:0732-8303    

DOI:10.1080/07328309508005395

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor